As radiotelephones became smaller manufacturers started adding batteries to the radiotelephones to make them truly portable. Most efforts at reducing power or current drain have concentrated on reducing the power the individual components draw. While this is helpful, power is often wasted by having the radiotelephone on when the user does not expect or want to receive any phone calls.
One solution has been to add a real time clock to the radiotelephone and have turn on and turn off times. The user then defines a time at which his radiotelephone is automatically turned off, such as 9:00 PM. The user can also a define a time when his radiotelephone is turned on to receive calls, such as 7:00 AM. This allows the user to define a period of time in which he will not receive phone calls without having to remember to turn off the radiotelephone. This also saves battery power since the radiotelephone is not accidentally left on all night.
However, many circumstances exist where the user may want his radiotelephone automatically to turn off that are not related to the time of day. For instance, many user's do not wish to receive any phone calls on their radiotelephone, but only want to place out bound calls. They may wish to do this to extend the operating time between charges or to save money. Presently, the user then has to remember to turn off the radiotelephone when he is done placing calls to achieve this goal. When the user forgets to turn off his radiotelephone in these situations, he significantly limits the time between battery charges. In other cases, the user may not wish to receive phone calls when he is outside the range of his home base. This is known as roaming. Roaming charges can add substantially to user's monthly bill and leaving the radiotelephone on unnecessarily limits the time between charges.
Thus there exists a need for radiotelephone that automatically turns off, when the user does not wish to receive in bound calls or when his radiotelephone is in the roam mode.